Commonly assigned U.S. Pat. No. 4,079,344, discloses a portable ground fault circuit interrupter (GFCI) device which can be plugged into any conventional wall outlet receptacle to provide personnel ground fault protection for a load circuit plugged into it. With this configuration, the GFCI device can simply be unplugged from one receptacle and plugged into another receptacle at a location convenient to the load circuit for which ground fault protection is desired. Basically, the portable GFCI device disclosed in this patent comprises a set of electrical connector blades or prongs which plug into a conventional receptacle, a relay, and a GFCI receptacle device, such as disclosed in commonly assigned U.S. Pat. No. 4,010,432. This GFCI receptacle device is designed to be installed in essentially dedicated fashion in a receptacle box in place of a conventional outlet receptacle. Thusly installed, ground fault protection is afforded any load circuit plugged into its receptacle sockets. In the event of a ground fault, the resulting current imbalance produces a ground fault signal in the secondary of a differential transformer. This ground fault signal is processed pursuant to developing a triggering signal on the gate of a silicon controlled rectifier connected in an energization circuit for a trip solenoid. Upon energization of this solenoid, its plunger defeats a mechanical latch holding circuit interrupting contacts closed, and the contacts consequently spring open to interrupt the load circuit.
In the portable GFCI device configuration disclosed in U.S. Pat No. 4,079,344, the GFCI receptacle is wired to the connector blades through normally open contacts of the relay. The inclusion of this relay serves as a safety measure to insure that the receptacle into which the portable GFCI device is plugged does not have a discontinuity in the neutral side of the power circuit feeding it. It will be appreciated that the existence of such a discontinuity would deny power to the GFCI receptacle ground fault signal processing circuitry, as well as the trip solenoid, and yet, but for the relay, the hot line side of the wall receptacle would be connected through to the GFCI receptacle sockets and thence to any load circuit plugged thereinto. In this situation, the potential for an electrical shock exists for a person coming into contact with the hot line side of the load circuit and ground, but the GFCI receptacle would be incapable of effecting a circuit interruption. Since the relay cannot be energized to close its contacts and complete the circuit between the wall receptacle and the GFCI receptacle unless there is complete continuity of the power circuit feeding the wall receptacle, this potentially hazardous situation is avoided.
It is a principal object of the present invention to provide an improved portable GFCI device.
A further object is to provide a portable GFCI device which is compact in size, inexpensive to manufacture, and convenient to use.
Other objects of the invention will in part be obvious and in part appear hereinafter.